An aspirating smoke detector is a fire detection system composed of an aspirated smoke detector (ASD) and a pipe network. A fan inside the detector draws the air from the pipe. It is very common to find on the market devices with two (or more) channels and two (or more) fans, completely independent one from the other. In order to draw air and eventually smoke inside the detector, the pipe has to be properly drilled.
Every drilled opening in the pipe is a sampling point. For example, a sampling point can cover a single room. In this way, if the fire system should protect ten rooms, ten holes, or sample points, have to be present in the pipe network. It is well known that with an aspiration detector it is difficult to detect in a reliable way from which hole smoke has enter. In other words, considering the ten room example above, it is difficult to detect the room where the fire has developed.
In the prior art, it is known that a way to detect the active smoke sample hole or sample point (SSH), is to use a secondary fan inside the detector. This fan rotates in the opposite direction with respect to the main fan.
In brief, when the ASD indicates an alarm, the main fan is stopped and a secondary fan is turned on, and rotates in the opposite direction. The combination of air and smoke that caused the alarm would be eliminated from the pipe such that only clean air, without smoke, is present in the pipe. At this time, a timer is triggered inside the device and the fans return to normal operation (main fan running, aspirating smoke, secondary fan stopped). Air and smoke are introduced again into the pipe: when smoke is detected, the timer is stopped. By comparing this time interval with the transport time of all the holes in the pipe network, the SSH can be determined.